In a vehicle such as an automobile, generally, an airbag device is mounted to absorb an impact on an occupant by inflating and deploying an airbag inside the vehicle in an emergency such as collision or a rapid deceleration thereof. Generally, an airbag device has an airbag that is folded during a normal state and is inflated and deployed in an emergency, an inflator that supplies gas to the airbag, a retainer that holds the airbag and the inflator, and an airbag cover that covers the airbag.
At a time of collision or a rapid deceleration of the vehicle, the airbag is inflated by being supplied gas from the inflator to the airbag and the airbag cover is opened, and the airbag is discharged into the vehicle, and then the airbag is inflated and deployed. Particularly, in a case of a passenger airbag device, the airbag is mounted inside an opening portion formed in the instrument panel and is inflated and deployed in a space surrounded by the instrument panel, a windshield (a front window) and an occupant.
If an obstacle exists in the inflation and deployment space of the airbag, the airbag collides with the obstacle and a posture (for example, an orientation or a position) thereof is collapsed so as not to inflate and deploy the airbag as planned. Thus, for example, as described in Japanese Unexamined Patent Application Publication No. 2005-14864 or Japanese Unexamined Patent Application Publication No. 2007-38713, an airbag capable of avoiding an obstacle is already proposed.
For example, in the airbag described in Japanese Unexamined Patent Application Publication No. 2005-14864, if the airbag comes into contact with the obstacle when the airbag is inflated and deployed, a variable vent hole is held in an open state so as to adjust an internal pressure thereof and thus the inflation and deployment of the airbag is stabilized. Further, the airbag described in Japanese Unexamined Patent Application Publication No. 2007-38713 is configured to include a sub-bag portion configuring a sub-chamber on a lower side of the airbag, and to suppress the impact by housing the obstacle adjacent to the instrument panel from the opening portion into the sub-chamber.